Electric incandescent lamp



March 12, 1935. A. E. CHAPMAN ELECTRIC INCANDESCENT LAMP Filed Nov. 19, 1932 2 Sheets-Sheet l March 12; 1935.

A. E. CHAPMAN ELECTRIC INCANDESCEI IT LAMP Filed Nov. 19, 1932 Z'Sheets-Sheet 2 Patented Mar. 12, 1935 UNITED STATES PATENT OFFICE Application November 19, 1932, Serial No. 643,510

In Great Britain June 8, 1932 2 Claims.

This invention relates to an improved mounting of the filament of an electric incandescent lamp in which the filament is supported in its central position within a long tube or within a tubular member which is bent to form letters or other characters or curved in any desired shape for decorative purposes.

The straight or curved filament, which may be elongated or spiralized, is supported within the tubular member on a longitudinally flexible member provided with lateral stays throughout its length or at a small number of points suitably spaced apart, which stays are secured to the said longitudinal member in an insulated manner by means of glass beads or the like, which may be fused to the longitudinal supporting member and to which the said stays are fused or otherwise attached,- the glass beads or the like serving at the same time to keep the longitudinal supporting member and all the stays. 3

The main object of the invention is to reduce shadows to a minimum, which may be produced directly by the mounting of the physical structure within the lamp with respect to the filament and indirectly by the contact of the physical structure with the innerwall of the lamp which, in the case of the lateral stays generally produces, owing to heat conductivity, carbon depositions on the'inner wall of the vessel, thus forming shadows.

With this object in view, the main feature of the invention consists in using straight lateral stays which make contact with the inner wall of the vessel solely at the actual tips of the stays, the contact thus being merely a point contact.

In order further to reduce the shadows to the lowest possible minimum, the glass beads referred to are preferably slightly pear-shaped and they are fused on the longitudinal supporting member with their narrow end lying against the inner wall of the tube, the longitudinal member being at a distance of about one third from the said narrow end.

The stays, of which one or more, but preferably two, are employed, are fused into the large end of the pear-shaped glass beads, penetrating therein to a depth of about one third, so that there is a depth of glass insulation of about one third of the length of the bead, between the stays and the longitudinal supporting member.

Triangular glass discs may be used instead of the pear-shaped beads, the longitudinal supporting member and the stays being fused therein at approximately the same depths as in the case of the glass beads.

The tubular member which contains the filament and which may be evacuated or gas-filled, may be of any desired cross-section and be made of silica; glass, or other suitable transparent or translucent material, of any desired color or combination of colors, or colorless. The vessel may be coated with an opalizing, coloring or reflecting medium on any portion of its surface.

The longitudinal supporting member may be made of any suitable material, preferablyof molybdenum or other" flexible wire, metallically continuous or broken at intervals and joined by insulators. The longitudinal supporting member may serve as a return conductor, in which case it is preferably insulated along its whole length.

The supporting stays, preferably made of molybdenum or other flexible wire, may, be attached to each or each alternate glass bead or disc throughout the whole length of the longitudinal supporting member, either prior to or after the attachment of the beads or discs o the said supporting member.

Instead of the glass beads or discs being secured to the longitudinal supporting member and the lateral stays by fusion, the attachment may be eifected by cementing or in any other suitable way.

The stays may be oxidized or roughened at the portion inserted in the glass bead or disc to increase the security of the attachment, and their tips may be rounded, smoothed, capped or suitably impregnated to avoid scratching of the inner wall of the filament container when the structure is inserted therein and in order further to reduce shadows to a minimum.

The actual filament supports which consists preferably of tungsten wires formed with pinched loops or pigtails and may be attached to all the glass beads or discs or only to some of them, may be oxidized or otherwise roughened at the portion where they are fused or otherwise attached to the beads or discs, being preferably disposed at equal distances apart, irrespective of the positions of the lateral stays, and in such a manner that .the filament comes to lie in the centre of the. tubular container.

According to a modification the filament supports are alternatelyslightly staggered and the pinched loops or pigtails at their tips reversed along the whole length, or a portion, of the longitudinal supporting member, whereby the filament sag is reduced to a minimum and wearing off of the filament at the points of support is avoided. The structure hereinbefore described may be used for the mounting of one, two, or more filaments, either in a straight or in a zig-zag form, or interlaced, coiled, or in any other form, the filaments, when a number of them are employed, being connectedin series, parallel, or otherwise, and adapted to be operated separately or together.

Springs may be mounted at either or both ends of] the filament and/or longitudinal supporting member to maintain rigidity of alignment.

The electrical connections of the filament to the supply mains maybe made at any point or points throughout the tubular or other shape of containing member.

It is to be understood that instead of one single pigtail filament support being attached to a bead or disc, two or more such supports may be secured thereto in such a manner as to be insulated from one another, that some of the lateral stays may be so bent and formed with a pigtail" or pinch as to serve at the same time as anactual filament support, and that the details of construction may otherwise be modified without in any way departing from the spirit of the invention.

Figures 1-10 of the accompanying drawings illustrate diagrammatically and byway of example different modes of carrying the invention into effect.

Fig. 1 is part of an improved electric incandescent lamp of tubular form,

Figs. 2, 3 and 4 are three different constructions at the bend of a bent electric incandescent lamp,

Fig. 5 is a cross-section showing more particularly the construction and mounting of the lateral stays,

Fig. 6 is a cross-section of the vessel showing more particularly the support of the filament and its mounting.

Fig. 7 is a cross-section showing the support of three separate filaments,

Figs. 8 and 9 illustrate two different forms of construction of the ends of the tubes, and

Fig. 10 illustrates a construction of tube provided with a standard cap at one end.

Referring to the construction illustrated in Figure 1, a is a part of an elongated tube in which the filament b is supported centrally by means of a, supporting structure comprising a flexible, longitudinal wire 0 on to which are fused a number of glass beads d, e, to which lateral stays f and looped or pigtail filament supports 9 are respectively suitably attached. It and i are springs provided at the ends of the filament b and of the longitudinal supporting member c respectively, to take up the expansion that may take place with the increase in temperature of the filament and longitudinal supporting member respectively or the contraction thereof with decrease in temperature.

The tube a may be made of any desired length or of standard length, irrespective of voltage,'by suitably spiralizing the filament. Thus, for instance, it may have an approximate length, straight or curved, of 24 ins. for a supply circuit of 100-130 volts and approximately 48 ins. for a supply circuit of 200-260 volts. Further, the diameter of the tube may vary and the lateral stays and lcopedfilament supports may accordingly be made of difierent lengths.

The tube may be made of any desired shape and curvature the structure which supports the filament being sufficiently flexible to adapt itself to the contour of the tube simply by being pushed and pulled through the tube and then laterally adjusted by magnetically pulling on the structure with a magnet outside the tube.

Figures 2, 3 and 4 illustrate a bent portion of a tube showing three diflerent ways of mounting the filament-supporting structure therein by means of the flexible push-pull longitudinal supporting member, being magnetic or having magnetic attachments as at o. t

In Figure 2 the longitudinal supporting member 0 lies in the centre at the back of the containing vessel.

In Figure 3 the said longitudinal supporting member 0 lies near the inner end of the tube, whilst in Figure 4 it lies near the outer bend thereof.

It is to be understood that the lateral stays may be made 0! magnetic material or have magnetic attachments thereon.

These arrangements may be used in connection with tubular vessels having any combination of curvatures.

Referring to Figure 5, it will be seen that the lateral stays f penetrate into the pear-shaped glass head at to a depth of about one-third of the bead and that their free ends abut against the wall of the containing vessel a. It will also be seen that the supporting longitudinal member 0 lies at a distance of about one-third of the whole length of the pear-shaped head (1 and that the smaller end of the latter abuts against the wall of the containing vessel a.

Referring to Figure 6, it will be seen that the filament 1) lies centrally within the vessel a, being maintained in this position bythe loop or pigtail Q1 of the filament support g, which penetrates into the glass bead e to a depth of about onethird of the length of the latter.

Figure 7 shows a bead g provided with three P gtails 91, 9'2 and g; which support three separate filaments b1, b2, b3. In this case the filament supports 9' have been shown attached to a circular disc at instead of a pear-shaped bead.

Figures 8 and 9 illustrate two different forms of construction of the ends of the tubes containing the filament and its support.

Figure 8 illustrates a side insertion of the foot or pinch a whilst Figure 10 illustrates an end insertion of the foot or pinch 7 of the tube. The same reference letters have been used as in connection with Figure 1, including h and i, which show the springs provided at the end of the filament, b and longitudinal support c respectively to maintain rigidity of alignment.

Figure 11 illustrates a construction of tube provided with a standard cap at one end and in which the supporting member also serves as a return conductor. The tube a is provided at one end with a standard connecting cap it, the two contacts of which are connected to one end of the filament b and one end of the supporting longitudinal member 0 respectively, their two other ends being electrically connected together at i. m are insulating members around the supporting longitudinal member 0. The end 11 of the vessel :1 may be finished in the form of a sandle or in any other desired shape.

.What I claim is:

1. An electric incandescent lamp of tubular form comprising a tubular vessel, a longitudinal supporting wire in said vessel, filament supports, afilament ori said supports, lateral stays having substantially pointed ends engaging the inner wall of said vessel solely at their pointed ends, glass beads connecting the filament supports and the lateral stays with the supporting wire, said glass beadsbeing pointed and disposed with their wider ends arranged inwardly and receiving the filament supports and lateral stays, the pointed ends of the beads abutting against the inner wall of said vessel.

2. An electric incandescent lamp as claimed in claim 1, characterized in that the substantially pointed ends of the stays engaging the inner wall of the tubular vessel are rounded and polished.

ALBERT EDWARD CHAPMAN.- 

